The invention relates to a method for filtering and separating flow media by means of membranes, including a substantially pressuretight housing in which a plurality of membranes is disposed, at least one inlet for the flow medium that is carried into the apparatus and that is to be separated, and at least one outlet for the permeate discharged from the apparatus and for the discharged retentate, the membranes being embodied on the order of membrane cushions, which have an opening region for the emergence of the permeate collecting in the membrane interior, and to an apparatus for filtering and separating flow media by means of membranes, including a substantially pressuretight housing in which a plurality of membranes is disposed, at least one inlet for the flow medium carried into the apparatus and to be separated, and at least one outlet for the permeate discharged from the apparatus and an outlet for the discharged retentate, the membranes being embodied on the order of membrane cushions, which have an opening region for the emergence of the permeate collecting in the membrane interior.
A method and an apparatus with which such a method can be performed is described for instance in European patent application EP A 1 445 013, where the apparatus is embodied in conjunction with an actual separator unit embodied in the form of a so-called winding membrane, which can be received in a pressuretight housing.
The membrane elements used there, which are commonly embodied in the form of so-called membrane cushions, which in the profession are also called a cushion membrane or membrane pockets, are adapted to the particular separation purpose with regard to the medium to be separated, and also with regard to its size (membrane surface area), and the actual substance-selective membranes that form the membrane cushions are likewise selected specifically for the separation purpose for the medium to be separated.
In pressure-driven separation techniques using pressure, a distinction is made among filtration, ultrafiltration, nanofiltration, and reverse osmosis. These pressure-driven separation techniques partly overlap, so that in the profession, a strict separation is considered only theoretically, with a view to the operative physical mechanism of the substance separation taking place in a membrane. Nevertheless, the aforementioned approximate classification—see Membrantrennverfahren, Ultrafiltration and Umkehrosmose [Membrane Separation Methods, Ultrafiltration and Reverse Osmosis] by Robert Rautenbach, published by Salle+Sauerländer in 1981—is commonly employed.
Substance separation by means of membranes has gained entry into nearly all areas of commercial business and extends for instance from substance separation in marine equipment, such as ships and drilling platforms that are set up or anchored on the sea, to the field of seawater desalination for producing water for industrial use and fresh water and for instance to the separation of water leaching out from garbage dumps or from commercial and community wastewater treatment, plants.
Many of these liquid flow media are composed of a varied mixture of different liquid components, sometimes even mixed with gaseous components, for which until now, for every desired separation product after it has gone through a separation method, a particular apparatus with which a separation method can be performed, or a product-specific separation device, has had to be furnished. As can readily be appreciated, this entails not only considerable expense for equipment but also complicated controls for the methods that must be used or performed for separating a complex mixture of substances. Many of the substances to be separated from a mixture of substances have to be separated out from a mixture of substances to be separated by using different separation mechanisms as in the above classification when a particular method for separating certain substances from the mixtures of substances to be separated is unsuitable, and only a different method leads to success. Until now, even for different substances in a substance mixture that belong to the same group of substances chemically and/or physically that are to separated out from the total mixture, separation was possibly only by one method of substance separation, but not by another.
Another factor, as already indicated above, is that until now, with flow media of complex composition, separation of the intermediate products can be achieved by repeated passages in succession through apparatuses that are each directed to the particular desired product to be separated. Not only does this entail the aforementioned great expense for equipment; it is also very time-consuming and requires a considerable expenditure of energy.
It is therefore the object of the invention to create a method with which various products, which are each accessible only to different separation mechanisms, can be separated in a single method operation from a substance mixture that is complicated to separate, and the method entails little expense for equipment, and an apparatus with which such a method can be performed does not need to be retrofitted, and hence the method can be performed quickly and economically.